The technology of fluid catalytic cracking and related processes for upgrading gas oils to gasoline product has been a subject of study since early 1940. As new experience was gained in operating and design parameters, new catalyst compositions were developed which furthered refinement of known operating technology and combinations thereof. The development of highly active crystalline zeolite conversion catalysts opened the door to a new era of technology requiring further development and refinement to optimize efficiency of the operation and combinations therewith. The present invention is concerned with an improved combination operation which relies upon crystalline zeolite structures varying considerably in physical properties to upgrade higher boiling hydrocarbons to gasoline boiling product. The present invention is directed to an improvement on the combination of U.S. Pat. No. 3,759,821 issued Sept. 18, 1973. In this patent there is disclosed the cracking of gas oil boiling hydrocarbons to produce cracked gasoline product which is separated to recover a C.sub.7 + gasoline fraction thereafter octane improved by passage over a ZSM-5 type of catalyst.